As the state attempts to reach the goal of producing one-third of its electricity from wind and solar sources by 2020, more reliable sources of traditional power will be needed as a backup.

Solar and wind advocates reject those concerns. They say renewables can provide their own reserve cushion because solar and wind generators will be spread across vast areas of the state. If wind power is down in one region, it might be up in another. If wind power is down statewide, desert sunshine might boost solar.

On the day last month when wind energy provided just 33 megawatts of power statewide, a brilliant sun spiked solar plant output.

The independent system operator "likes to show these frightening graphs for shock value," said Nancy Rader, executive director of the California Wind Energy Assn.

Edward Randolph, director of the Public Utility Commission's energy division, said the independent system operator understandably wants more reserves because its primary focus is on the reliability of the system. The PUC is focused on cost. If there is an immediate problem with reserves, the PUC can order utilities to make more available. And in three to five years, batteries, flywheels or other new technology can provide storage that would make reserves much less necessary, he said.

The problem with reserves is an outgrowth of a separate decision by the powerful California Water Quality Control Board. The board last year essentially ordered 19 gas-fired generating plants up and down the coast to close by 2020 because their cooling intake pipes suck in and kill fish.

The agency concedes that it does not know the extent of the fish kill. Virginia-based AES conducted a study of its plant in Huntington Beach and found that just four pounds of fish and other marine life per day were lost — about what one pelican eats. Other plants do kill more fish, AES acknowledged.

Jonathan Bishop, chief deputy director of the water board, said the plants are so old and inefficient that they need to be replaced in any case. And if serious grid problems develop, the deadline can be extended, he said.

AES operates three of the doomed plants in Southern California. Its Alamitos Power Plant in Long Beach is among the largest thermal generating plants in the nation, producing 2,000 megawatts of power. The size and location of the plant make it a critical part of keeping line voltage stable for Southern California.

The company would like to rebuild the plant to comply with the water board's regulation, but the cost is estimated at $2 billion.

"We see there is a path forward where those doomsday scenarios don't have to become true, but a lot has to fall into place, said Stephen O'Kane, the AES executive in charge of permitting and regulatory approval in Southern California. He said the biggest question is, "Who is going to pay for it?"

O'Kane noted that another regulatory agency, the South Coast Air Quality Management District, will impose a 10% fee to redevelop the plant, adding $200 million to the cost, which would eventually be passed on to consumers.

Amid the tough regulatory environment, Calpine and AES both say state regulators must increase the compensation for reserve power — for keeping their equipment ready to produce power on a moment's notice.

California will need to make billions of dollars in investments to prevent electrical grid problems, which will increase costs for both residents and businesses, said Jan Smutny-Jones, executive director of the Independent Energy Producers Assn., a California trade group representing electricity generators.

The renewable energy mandate, coupled with the closure of coastal power plants, have created "one big happy dysfunctional system," he said.